Neurosurgical outcome studies of traumatic brain injury (TBI) identify strikingly high rates of mortality and morbidity in infants and young children. As few prospective longitudinal outcome studies have been completed, the objective of this proposal is to examine factors influencing the outcome of infants and young children who sustain TBI from either physical child abuse (inflicted) or accidental (noninflicted) causes. To more clearly dissociate the effects of age, external cause of injury, and severity of brain injury, we propose to study the following Specific Aims: 1) tom characterize the influence of age at injury, inflicted versus noninflicted TBI, structural damage to brain regions, and disturbance of consciousness on outcome; 2) to relate family characteristics and executive function deficits to the development of social competence, self-regulation, and academic skills; and 3) to identify relationships of regional and global cerebral volume based on quantitative MRI to outcome domains. We propose 3 interrelated prospective, longitudinal neurobehavioral follow-up studies of young children sustaining inflicted or noninflicted TBI. Study 1 will follow the cohort of children enrolled in the initial funding period to assess the long-term effects of inflicted and noninflicted TBI sustained from 0-71 months of age on the expanded outcome domains. Study 2 will enroll a new cohort of children ages 0-35 months with either inflicted or noninflicted TBI to address the influence of age, injury characteristics, and quantitative neuroimaging findings on the developmental trajectory of cognitive and social outcomes. Study 3 will examine the relationship between quantitative neuroimaging findings, executive functions, and the development of academic skills in children sustaining noninflicted TBI between 36-59 months. Studies 2 and 3 will follow children at baseline, 3, 12, and 24 months after injury; quantitative MRIs will be obtained at 3 and 24 months. Noninjured comparison children from sociodemographic backgrounds comparable to the injured children will be recruited for each study and followed on the same schedule. Current knowledge will be extended by assessment of 1) a multifactorial index characterizing severity of TBI, 2) dissociation of effects of age at injury and cause of injury, 3) relationships between regional cerebral volume and outcome domains, 4) the impact of early TBI on the developmental trajectory of executive functions, and 5) relationships between family and injury variables that moderate cognitive, behavioral, and affective development.